The invention relates to electric machines having external or hybrid excitation, in particular methods for operating electric machines of this type.
Synchronous motors are widely used as electronically commutated electric machines. Said motors are highly suitable for many applications, but, in particular in the partial-load range, have the disadvantage that the field attenuation necessary there is very complicated to realize. In contrast thereto, in the case of electric machines having external or hybrid excitation, the field attenuation is achieved very simply by a reduction of the exciter magnetic field. In the case of electric machines having external excitation, the exciter magnetic field is generated with the aid of a separate exciter winding, while in the case of electric machines having hybrid excitation, the exciter magnetic field is generated both by permanent magnets and with the aid of a separate exciter winding.
The exciter winding serves to direct a static magnetic field at a rotor body which collects the magnetic flux and directs it via the rotor poles 24 in the direction of the stator. In previous motors having external or hybrid excitation, the circuitry outlay is increased on account of the additional exciter winding and, both outside and within the electric machine, a corresponding wiring is necessary in order to provide a direct current through the exciter winding. The outlay during production and use of such electric machines having external or hybrid excitation is significantly increased as a result.
Therefore, it is a object of the present invention to reduce the outlay for interconnecting the exciter winding in electric machines having external or hybrid excitation. Furthermore, it is an object of the invention to provide a method for operating electric machines having external or hybrid excitation.